1. Field of the Invention
The subject invention resides in apparatus for feeding and controlling ringing currents in line circuits of telecommunication and, in particular, telephone exchange systems. The line circuits may be of the type wherein the feeding of ringing currents to subscriber circuits is effected via an electronic device connected between the ringing current source and the line circuit feeding junction.
2. Description of the Prior Art
There are known telephone exchange systems in which the ringing of a subscriber is effected through feeding a low-frequency ringing current into the subscriber loop. The removal of the handset at the called subscriber station is sensed through detection of the changing condition in the particular subscriber loop. The ringing current may, for instance, be fed into the subscriber line in the form of a half-wave signal, and the connection of the ringing current may advantageously be effected with controlled semiconductors.
In order to keep the switching equipment as simple as possible, it is advantageous to effect a direct feeding of the ringing current into the subscriber line and to the subscriber to be called. This direct feeding technique resides in the fact that a controlled switching device is disposed between the source issuing the calling signal and the feeding junction in the line circuit.